You'll need some trim removal tools.
Move the power mirror full up, then place a piece of cloth at the bottom of the trim, pry up on the back of the glass toward you and work your way around. 8 clips total.
Then you'll pry the upper inside trim out. 6 clips, again working your way around.
The glass for the bulb assembly is held on by two clips. Pop it out, then replace the bulb.
If you have heated mirrors, don't forget about the plug. It's on the upper side toward the car.